a) Field of the Invention
The present invention pertains generally to a ball joint for motor vehicles, and more particularly to a unitized boot seal formed of an elastically deformable material in which a metallic sealing element is provided adjacent the boot seal to shaft interface to prevent contamination of the sealed area.
b) Description of Related Art
Ball joints are commonly used as a pivotal coupling for allowing two members to angularly move with respect to each other. After a period of time, the ball joint may be subject to wear as a result of contact by one or both members. This is especially true if the ball joint is surrounded by a rubber boot seal that is continually abraded by a mating member during motion, thereby resulting in the aforementioned wear and the formation of an opening in the boot. When this wear occurs in the boot seal, contamination in the form of water, dust and road salt may enter the opening causing wear to the joint connection. Moreover, the interface between the boot and the ball joint members tends to become separated from the member(s) during prolonged use, and it is common for contamination to intrude upon the sealed area after such prolonged use.
One typical use for ball joints is in a front steering assembly of a motor vehicle, and specifically in the tie rod end joint. Tie rod end joint wear is a common warranty item for front steer axle assemblies. In operation, a tie rod cross tube has a ball joint assembly mounted at each end (i.e. the tie rod end joint) to which a side tie rod arm is coupled. This ball joint permits the steering knuckle, which is connected to a tie rod arm, to articulate with respect to the tie rod cross tube.
A boot seal often surrounds the ball joint, protecting it from wear as well as sealing the ball joint connection area from environmental factors and provide a means to retain ball joint lubrication fluid. Again, the aforementioned wear is a result of abrasion by the tie rod arm of the steering knuckle against the ball joint and boot seal during articulation. Moreover, the boot tends to separate from the ball joint shaft during use, and contamination enters the sealed area as a result of such separation.
Retaining rings and protective covers have been used to prevent unwanted separation of the boot from the shaft or damage to the boot element. However, these conventional devices do not effectively protect the boot seal from damage or divert contamination away from the boot to shaft interface.
Excluding contamination from the ball joint is important to increase lubrication intervals, to eliminate the need for re-lube, to extend the serviceable life of a tie rod end joint, and to improve the performance of the joint through reduced wear. Existing tie rod assembly designs do not adequately prevent contamination at the rotating boot to arm boss interface and the boot to ball stud.
The surface of the steering knuckle is forged or rough machined, and such rough machine surface finish provide an inadequate surface for the seal interface to seal against contamination entry into the tie rod end.
Consequently, there is a need for a secondary sealing element for the boot seal of the tie-rod end ball joint adjacent the boot seal to arm boss interface to provide an adequate sealing surface for the boot and to divert contamination from the primary boot to ball stud and arm seal location.
The present invention provides a boot seal surface interface for adequately scaling the ball joint and for diverting contamination from the primary boot to ball stud and arm seal location, and the present invention provides a boot seal element for use in a steering assembly of a motor vehicle for protecting the boot seal of a tie rod end ball joint from contamination during articulation of the steering knuckle.
It is a further object according to the present invention to provide a secondary sealing portion for the boot seal of the tie rod end ball joint that is both manufacturing friendly and cost effective.
And it is a still further object according to the present invention to provide a secondary sealing portion of the boot seal element that does not impede the angular movement or rotation of the ball joint. Dynamic sealing during normal tie rod rotation and oscillation occurs between the sealing element and the tie rod boot.
In carrying out the above objects, features and advantages, the present invention provides a pivotal ball joint assembly which includes, generally, a metallic sealing surface adjacent the boot and a secondary sealing surface to act as an excluder keeping contamination away from the primary sealing interface.
The sealing member, made of metal or the like, is pressed onto the tapered portion of the ball stud during assembly. Once assembled, there is no relative motion between the knuckle, tie rod ball stud, and the metallic sealing surface. A static sealing area may be provided between the metallic sealing member, ball stud, and knuckle. For example, an adhesive may be used, an o-ring may be located in a groove provided in the knuckle, or an o-ring may be provided within a groove in the metallic sealing member.
The secondary sealing arrangement provides a path for contamination to be diverted from the primary boot to ball stud and arm seal location. The formed seal provides a labyrinth that makes it difficult for contamination to reach the boot seal/ball stud interface.
The above objects and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings wherein like reference numerals correspond to like components.